text: # vim: tabstop=4 shiftwidth=4 softtabstop=4
  
  # Copyright (c) 2012 OpenStack Foundation.
  # Administrator of the National Aeronautics and Space Administration.
  # All Rights Reserved.
  #
  #    Licensed under the Apache License, Version 2.0 (the "License"); you may
  #    not use this file except in compliance with the License. You may obtain
  #    a copy of the License at
  #
  #         http://www.apache.org/licenses/LICENSE-2.0
  #
  #    Unless required by applicable law or agreed to in writing, software
  #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  #    License for the specific language governing permissions and limitations
  #    under the License.
  
  from __future__ import print_function
  
  import gc
  import pprint
  import sys
  import traceback
  
  import eventlet
  import eventlet.backdoor
  import greenlet
  from oslo.config import cfg
  
  eventlet_backdoor_opts = [
      cfg.IntOpt('backdoor_port',
                 default=None,
                 help='port for eventlet backdoor to listen')
  ]
  
  CONF = cfg.CONF
  CONF.register_opts(eventlet_backdoor_opts)
  
  
  def _dont_use_this():
      print("Don't use this, just disconnect instead")
  
  
  def _find_objects(t):
      return filter(lambda o: isinstance(o, t), gc.get_objects())
  
  
  def _print_greenthreads():
      for i, gt in enumerate(_find_objects(greenlet.greenlet)):
          print(i, gt)
          traceback.print_stack(gt.gr_frame)
          print()
  
  
  def _print_nativethreads():
      for threadId, stack in sys._current_frames().items():
          print(threadId)
          traceback.print_stack(stack)
          print()
  
  
  def initialize_if_enabled():
      backdoor_locals = {
          'exit': _dont_use_this,      # So we don't exit the entire process
          'quit': _dont_use_this,      # So we don't exit the entire process
          'fo': _find_objects,
          'pgt': _print_greenthreads,
          'pnt': _print_nativethreads,
      }
  
      if CONF.backdoor_port is None:
          return None
  
      # NOTE(johannes): The standard sys.displayhook will print the value of
      # the last expression and set it to __builtin__._, which overwrites
      # the __builtin__._ that gettext sets. Let's switch to using pprint
      # since it won't interact poorly with gettext, and it's easier to
      # read the output too.
      def displayhook(val):
          if val is not None:
              pprint.pprint(val)
      sys.displayhook = displayhook
  
      sock = eventlet.listen(('localhost', CONF.backdoor_port))
      port = sock.getsockname()[1]
      eventlet.spawn_n(eventlet.backdoor.backdoor_server, sock,
                       locals=backdoor_locals)
      return port
  